Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 10-12 cup bundt pan thoroughly. Pour the dulce de leche or caramel sauce evenly into the bottom of the prepared bundt pan.
Step 2: Prepare the chocolate cake batter according to the package directions. Carefully pour the cake batter over the caramel layer in the bundt pan. Do not mix them.
Step 3: In a blender, combine the softened cream cheese, eggs, evaporated milk, sweetened condensed milk, and vanilla extract. Blend until the mixture is completely smooth and creamy, about 30-60 seconds.
Step 4: Carefully pour the blended flan mixture over the chocolate cake batter in the bundt pan. Again, do not stir or mix the layers.
Step 5: Place the bundt pan into a larger roasting pan. Carefully pour hot water into the roasting pan, ensuring it comes at least halfway up the sides of the bundt pan. This creates a water bath.
Step 6: Bake for 60-75 minutes, or until a knife inserted into the flan portion comes out clean and the cake is set. The baking time may vary, so keep an eye on it.
Step 7: Carefully remove the bundt pan from the water bath and let it cool on a wire rack for at least 1 hour. Then, refrigerate the Magic Flan Cake for a minimum of 6-8 hours, or preferably overnight, to ensure it is thoroughly chilled and set.
Step 8: Once chilled, run a thin knife or spatula around the inner and outer edges of the bundt pan to loosen the cake. Place your serving platter upside down over the bundt pan, and in one swift, confident motion, flip the cake over. Lift the bundt pan to reveal your perfectly layered Magic Flan Cake. Slice and serve chilled.